Tire

ABSTRACT

In a tire having a specified mounting direction, groove area ratios Rin and Rout in ground contact regions on the vehicle inner and outer sides, respectively, satisfy Rin&gt;Rout, average land portion areas Ain and Aout of intermediate regions Min and Mout on the vehicle inner and outer sides, respectively satisfy Ain&lt;Aout, the number of blocks Nin, Nout in the intermediate regions Min, Mout, respectively, satisfy Nin≥1.5×Nout, total sipe lengths Sin, Sout in the intermediate regions Min, Mout, respectively, satisfy Sin&lt;Sout, and sipes formed in the intermediate region Mout have a three-dimensional structure in a range of 70% or more of a sipe length.

TECHNICAL FIELD

The present technology relates to a tire in which a mounting directionwith respect to a vehicle is specified and particularly relates to atire that can provide improved wear resistance performance and snowperformance in a well-balanced manner while dry performance and wetperformance are improved.

BACKGROUND ART

In a known tire tread pattern, lateral grooves extending in a tire widthdirection are formed in land portions defined by a plurality of maingrooves. Providing such lateral grooves ensures drainage properties andexhibits wet performance (steering stability performance on wet roadsurfaces for example) (see, for example, Japan Unexamined PatentPublication No. 2007-230251 A). Unfortunately, many lateral groovesdisposed in a tread portion to improve the wet performance decrease therigidity of the land portions, thus decreasing dry performance (steeringstability performance on dry road surfaces, for example).

Providing sipes in a tread pattern ensures snow traction and exhibitssnow performance (steering stability performance and braking performanceon snow-covered road surfaces, for example). Unfortunately, increasing agroove area of the sipes decreases block rigidity, thus decreasing thedry performance and the wet performance. Further, a larger amount ofsipes decreases the block rigidity, making it difficult to achieveexcellent wear resistance performance.

SUMMARY

An object of the present technology is to provide a tire that canprovide improved wear resistance performance and snow performance in awell-balanced manner while dry performance and wet performance areimproved.

A tire according to an embodiment of the present technology to achievethe object described above includes at least four main grooves extendingin a tire circumferential direction and a plurality of rows of landportions defined by the main grooves in a tread portion, the landportions located on a tire equator line are formed of a block row or arib row, and a mounting direction with respect to a vehicle isspecified. In the tire, a plurality of lateral grooves extending in atire width direction is formed in an intermediate region between a maingroove of the main grooves located on an innermost side in the tirewidth direction and a main groove of the main grooves located on anoutermost side in the tire width direction on a vehicle inner side ofthe tread portion from the tire equator line as a boundary and anintermediate region between a main groove of the main grooves located onan innermost side in the tire width direction and a main groove of themain grooves located on an outermost side in the tire width direction ona vehicle outer side of the tread portion from the tire equator line asthe boundary, the lateral grooves have a groove width of 2 mm or moreand a groove depth of 50% or more of a maximum depth of the maingrooves, the intermediate region on the vehicle inner side and theintermediate region on the vehicle outer side each include 50 or moreblocks defined by the lateral grooves, a plurality of sipes extending inthe tire width direction is formed in each of the blocks in theintermediate region on the vehicle inner side and the blocks in theintermediate region on the vehicle outer side, a groove area ratio Rinin a ground contact region on the vehicle inner side and a groove arearatio Rout in a ground contact region on the vehicle outer side satisfya relationship Rin>Rout, an average land portion area Ain in theintermediate region on the vehicle inner side and an average landportion area Aout in the intermediate region on the vehicle outer sidesatisfy a relationship Ain<Aout, the number of blocks Nin in theintermediate region on the vehicle inner side and the number of blocksNout in the intermediate region on the vehicle outer side satisfy arelationship Nin≥1.5×Nout, a total sipe length Sin in the intermediateregion on the vehicle inner side and a total sipe length Sout in theintermediate region on the vehicle outer side satisfy a relationshipSin<Sout, and the sipes formed in the blocks in the intermediate regionon the vehicle outer side have a three-dimensional structure in a rangeof 70% or more of a sipe length.

According to the present technology, the tire in which a vehiclemounting direction is specified has the groove area ratio Rin in theground contact region on the vehicle inner side and the groove arearatio Rout in the ground contact region on the vehicle outer sidesatisfying the relationship Rin>Rout. Thus, differentiating the groovearea ratios on the vehicle inner side and on the vehicle outer sideallows dry performance (steering stability performance on dry roadsurfaces) and wet performance (steering stability performance on wetroad surfaces) to be improved. In addition, in the intermediate regionon the vehicle inner side and the intermediate region on the vehicleouter side including 50 or more blocks, the average land portion areaAin on the vehicle inner side and the average land portion area Aout onthe vehicle outer side satisfy the relationship Ain<Aout, the number ofblocks Nin on the vehicle inner side and the number of blocks Nout onthe vehicle outer side satisfy the relationship Nin≥1.5×Nout, and thetotal sipe length Sin on the vehicle inner side and the total sipelength Sout on the vehicle outer side satisfy the relationship Sin<Sout.This relatively increases a sipe component in the intermediate region onthe vehicle outer side, allowing snow performance (steering stabilityperformance and braking performance on snow-covered road surfaces) to beimproved. When a sipe component in the intermediate region on thevehicle inner side is relatively large, the snow performance (tractionperformance at the time of starting, in particular) can be improvedwhereas wear resistance performance is likely to be degraded. In view ofthis, an amount of sipes in the intermediate region on the vehicle outerside are increased more than an amount of sipes in the intermediateregion on the vehicle inner side, and the amount of sipes on the vehicleinner side and the vehicle outer side is adjusted to improve the wearresistance performance. Furthermore, the sipes formed in the blocks inthe intermediate region on the vehicle outer side have thethree-dimensional structure in a range of 70% or more of the sipelength, thus the reduction in block rigidity due to sipes provided issupplemented, and the snow performance and the wear resistanceperformance can be improved in a well-balanced manner.

In the tire according to an embodiment of the present technology, theaverage land portion area Ain in the intermediate region on the vehicleinner side and the average land portion area Aout in the intermediateregion on the vehicle outer side preferably satisfy a relationship1.5×Ain≤Aout≤3.0×Ain. This can effectively improve wear resistanceperformance and snow performance.

The total sipe length Sin in the intermediate region on the vehicleinner side and the total sipe length Sout in the intermediate region onthe vehicle outer side preferably satisfy a relationship1.3×Sin≤Sout≤2.0×Sin. This can effectively improve wear resistanceperformance and snow performance.

The groove area ratio Rin in the ground contact region on the vehicleinner side and the groove area ratio Rout in the ground contact regionon the vehicle outer side preferably satisfy a relationship3%≤Rin−Rout≤8%. This can improve wear resistance performance and snowperformance in a well-balanced manner while maintaining dry performanceand wet performance.

The sipes formed in the intermediate region on the vehicle inner sideand the sipes formed in the intermediate region on the vehicle outerside are preferably inclined in opposite directions with respect to thetire width direction. This can effectively improve snow performance.

An inclination angle of the sipes formed in the intermediate region onthe vehicle inner side and an inclination angle of the sipes formed inthe intermediate region on the vehicle outer side preferably range from20° to 65°. This can effectively improve snow performance.

The tire according to an embodiment of the present technology ispreferably a pneumatic tire but may be a non-pneumatic tire. In a caseof a pneumatic tire, the interior thereof can be filled with any gasincluding air and inert gas such as nitrogen.

In the present technology, the ground contact region is a region in thetire width direction that corresponds to a maximum linear distance (tireground contact width) in the tire width direction on a contact surfaceformed on the flat plate, when the tire is filled with air pressurecorresponding to a maximum load capacity specified for each tireaccording to the standards (JATMA (The Japan Automobile TyreManufacturers Association, Inc.), TRA (The Tire and Rim Association,Inc.), ETRTO (The European Tyre and Rim Technical Organisation), and thelike) based on the tire and is placed vertically on a flat plate in astationary state and when a load equivalent to 80% of the maximum loadcapacity is applied. In a case of a non-pneumatic tire, a ground contactregion is specified under similar load conditions. The groove area ratioRin in the ground contact region on the vehicle inner side is apercentage (%) of a total area of groove portions included in a groundcontact region on the vehicle inner side of the tread portion to a totalarea of the ground contact region on the vehicle inner side of the treadportion. The groove area ratio Rout in a ground contact region on thevehicle outer side is a percentage (%) of a total area of grooveportions included in the ground contact region on the vehicle outer sideof the tread portion to a total area of the ground contact region on thevehicle outer side of the tread portion. The average land portion areaAin in the intermediate region on the vehicle inner side is a value (mm²per the number of blocks) obtained by dividing the total area (mm²) ofthe blocks included in the intermediate region on the vehicle inner sideby the number of blocks Nin in the intermediate region on the vehicleinner side. The average land portion area Aout in the intermediateregion on the vehicle outer side is a value (mm² per the number ofblocks) obtained by dividing the total area (mm²) of the blocks includedin the intermediate region on the vehicle outer side by the number ofblocks Nout in the intermediate region on the vehicle outer side. Thetotal sipe length Sin of the intermediate region on the vehicle innerside is a sum of the sipe lengths of the sipes formed in theintermediate region on the vehicle inner side on the road contactsurface. The total sipe length Sout of the intermediate region on thevehicle outer side is a sum of the sipe lengths of the sipes formed inthe intermediate region on the vehicle outer side on the road contactsurface.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a meridian cross-sectional view illustrating one example of apneumatic tire according to an embodiment of the present technology.

FIG. 2 is a plan view illustrating a tread portion of the pneumatic tireof FIG. 1 .

FIGS. 3A and 3B are plan views illustrating sipes formed in a blockincluded in an intermediate region of the tread portion, FIG. 3Aillustrates sipes in an intermediate region on a vehicle inner side, andFIG. 3B illustrates sipes in an intermediate region on a vehicle outerside.

FIGS. 4A and 4B are side views illustrating a sipe formed on a block inthe intermediate region on the vehicle outer side of the tread portion,FIG. 4A is a perspective view, and FIG. 4B is a side view illustratingan inner wall surface of the sipe.

DETAILED DESCRIPTION

A configuration according to an embodiment of the present technologywill be described in detail below with reference to the accompanyingdrawings. FIGS. 1 and 2 illustrate a pneumatic tire according to anembodiment of the present technology. In FIGS. 1 and 2 , CL denotes atire equator line.

As illustrated in FIG. 1 , a pneumatic tire according to an embodimentof the present technology has a specified mounting direction withrespect to a vehicle. “IN” indicates a region on an inner side from thetire equator line CL with respect to the vehicle when the tire ismounted on the vehicle (hereinafter referred to as “vehicle innerside”), and “OUT” indicates a region on an outer side from the tireequator line CL with respect to the vehicle when the tire is mounted onthe vehicle (hereinafter referred to as “vehicle outer side”). Thispneumatic tire includes an annular tread portion 1 extending in the tirecircumferential direction, a pair of sidewall portions 2 respectivelydisposed on both sides of the tread portion 1, and a pair of beadportions 3 each disposed on the inner side of the pair of sidewallportions 2 in the tire radial direction.

A carcass layer 4 is mounted between the pair of bead portions 3, 3. Thecarcass layer 4 includes a plurality of reinforcing cords extending inthe tire radial direction and is folded back around a bead core 5disposed in each of the bead portions 3 from a tire inner side to a tireouter side. A bead filler 6 having a triangular cross-sectional shapeand formed of a rubber composition is disposed on the outercircumference of the bead core 5.

On the other hand, a plurality of belt layers 7 are embedded on theouter circumferential side of the carcass layer 4 in the tread portion1. The belt layers 7 include a plurality of reinforcing cords that areinclined with respect to the tire circumferential direction, and thereinforcing cords are disposed so as to intersect each other between thelayers. In the belt layers 7, the inclination angle of the reinforcingcords with respect to the tire circumferential direction is set to arange of, for example, from 10° to 40°. Steel cords are preferably usedas the reinforcing cords of the belt layers 7. To improve high-speeddurability, at least one belt cover layer 8 formed by arrangingreinforcing cords at an angle of, for example, 5° or less with respectto the tire circumferential direction is disposed on an outercircumferential side of the belt layers 7. Organic fiber cords such asnylon and aramid are preferably used as the reinforcing cords of thebelt cover layer 8.

Note that the tire internal structure described above represents atypical example for a pneumatic tire, but the pneumatic tire is notlimited thereto.

As illustrated in FIG. 2 , at least four main grooves 9 extending in thetire circumferential direction are formed in the tread portion 1. InFIG. 2 , the main grooves 9 include a pair of main grooves 9A eachlocated on the innermost side in the tire width direction on the vehicleinner side and the vehicle outer side, a pair of main grooves 9B eachlocated on the outermost side in the tire width direction on the vehicleinner side and the vehicle outer side, and a main groove 9C locatedbetween the main groove 9A and the main groove 9B on the vehicle innerside.

In the tread portion 1, a plurality of rows of land portions 10extending in the tire circumferential direction are defined by the maingrooves 9, and these land portions 10 are further defined by a pluralityof lateral grooves 20 extending in the tire width direction to form aplurality of blocks 100. These blocks 100 form a plurality of sipes 30extending in the tire width direction.

Specifically, the land portions 10 include land portions 11 located onthe tire equator line CL, a pair of land portions 12 and 14 located onboth sides of the land portions 11, land portions 13 located on theouter side of the land portions 12 in the tire width direction; and apair of land portions 15 and 16 located on the outermost sides in thetire width direction. The land portions 11 (center land portions)located on the tire equator line CL are formed of a block row but may beformed of a rib row extending in the tire circumferential direction. Thelateral grooves 20 include lateral grooves 21 to 26 that define the landportions 11 to 16 respectively. The sipes 30 include sipes 31 to 36formed in the blocks 100 forming the respective land portions 11 to 16.

A region between the main groove 9A located on the innermost side in thetire width direction and the main groove 9B located on the outermostside in the tire width direction on the vehicle inner side of the treadportion 1 is an intermediate region Min, and a region between the maingroove 9A located on the innermost side in the tire width direction andthe main groove 9B located on the outermost side in the tire widthdirection on the vehicle outer side of the tread portion 1 is anintermediate region Mout. The intermediate region Min on the vehicleinner side and the intermediate region Mout on the vehicle outer sideeach include 50 blocks 100 or more on the tire circumference. Thelateral grooves 22 to 24 in the intermediate regions Min and Mout eachhave a groove width of 2 mm or more, and a groove depth of 50% or moreof the maximum depth of the main groove 9.

The sipes 32 and 33 formed in the blocks 100 in the intermediate regionMin (the land portions 12 and 13) on the vehicle inner side have oneends in communication with the main grooves 9 and have the other endsterminated within the blocks 100. Thus, the sipes 32 and 33 aresemi-closed sipes. The sipes 34 formed in the block 100 in theintermediate region Mout on the vehicle outer side (land portion 14)have both ends in communication with the main grooves 9. Thus, the sipes34 are open sipes. Furthermore, the sipes 32 and 33 in the intermediateregion Min on the vehicle inner side and the sipes 34 in theintermediate region Mout on the vehicle outer side are inclined at aninclination angle θ (see FIGS. 3A and 3B) with respect to the tire widthdirection.

The sipes 34 in the intermediate region Mout on the vehicle outer sideentirely or partially have a three-dimensional structure. Specifically,as illustrated in FIGS. 4A and 4B, in the block 100, a plurality of bentportions 40 bent in a direction (y direction) orthogonal to a sipeextension direction (x direction) at a plurality of portions in a sipedepth direction (z direction), are continuously formed in the sipeextension direction, to be in a zigzag shape on the road contactsurface. The bent portions 40 include a bent portion 41 of a protrudingform and a bent portion 42 of a recessed form. On a wall surface of oneside of the sipe 34, these protruding and recessed bent portions 41 and42 are alternately arranged, with the protruding and recessed bentportions 41 and 42 on the facing wall surface (not illustrated) on theopposite side being in the positional relationship opposite thereto.With the sipe 34 thus provided with the bent portions 40 bent in thetire circumferential direction, small blocks on both sides of the sipe34 are meshed with each other at the time of driving/braking to suppressthe deformation of the block 100, so that the block 100 can be preventedfrom flexing in the tire circumferential direction. The sipe length ofthe sipe 34 measured on the surface of the tread portion 1 is greaterthan the sipe length on a groove bottom, and the sipe length of the sipe34 gradually decreasing toward the groove bottom. The bent shape in thesipe 34 on the surface of and inside the block 100 is not limited to aparticular shape.

Further, the sipes 34 in the intermediate region Mout on the vehicleouter side have the three-dimensional structure in a range of 70% ormore of a sipe length L1 measured on the road contact surface in theextension direction. In other words, the percentage of lengths L2 and L3of portions of the sipe 34 without the three-dimensional structure (seeFIG. 3B) with respect to the sipe length L1 is less than 30%((L2+L3)/L1×100%). In the sipe 34, the portions (end portions of thesipe) without the three-dimensional structure include no bent portion 40inside the block 100, resulting in parallel wall surfaces formed.

In the tire described above, a groove area ratio Rin in the groundcontact region on the vehicle inner side and a groove area ratio Rout inthe ground contact region on the vehicle outer side satisfy therelationship Rin>Rout. In addition, in the intermediate region Min onthe vehicle inner side and the intermediate region Mout on the vehicleouter side, an average land portion area Ain on the vehicle inner sideand an average land portion area Aout on the vehicle outer side satisfythe relationship Ain<Aout. The number of blocks Nin on the vehicle innerside and the number of blocks Nout on the vehicle outer side satisfy therelationship Nin≥1.5×Nout. A total sipe length Sin on the vehicle innerside and a total sipe length Sout on the vehicle outer side satisfy therelationship Sin<Sout. The number of blocks Nin on the vehicle innerside and the number of blocks Nout on the vehicle outer side preferablysatisfy the relationship Nin≤3.0×Nout, indicating the upper limit.

The tire described above in which a vehicle mounting direction isspecified has the groove area ratio Rin in the ground contact region onthe vehicle inner side and the groove area ratio Rout in the groundcontact region on the vehicle outer side satisfying the relationshipRin>Rout. Thus, differentiating the groove area ratios Rin and Rout onthe vehicle inner side and on the vehicle outer side allows the dryperformance (steering stability performance on dry road surfaces) andwet performance (steering stability performance on wet road surfaces) tobe improved. In addition, in the intermediate region Min on the vehicleinner side and the intermediate region Mout on the vehicle outer sideincluding 50 or more blocks 100, the average land portion area Ain onthe vehicle inner side and the average land portion area Aout on thevehicle outer side satisfy the relationship Ain<Aout, the number ofblocks Nin on the vehicle inner side and the number of blocks Nout onthe vehicle outer side satisfy the relationship Nin≥1.5×N out, and thetotal sipe length Sin on the vehicle inner side and the total sipelength Sout on the vehicle outer side satisfy the relationship Sin<Sout.This relatively increases the sipe component in the intermediate regionMout on the vehicle outer side, allowing the snow performance (steeringstability performance and braking performance on snow-covered roadsurfaces) to be improved. When a sipe component in the intermediateregion Min on the vehicle inner side is relatively large, the snowperformance (traction performance at the time of starting, inparticular) can be improved whereas wear resistance performance islikely to be degraded. In view of this, an amount of sipes in theintermediate region Mout on the vehicle outer side are increased morethan an amount of sipes in the intermediate region Min on the vehicleinner side, and the amount of sipes on the vehicle inner side and thevehicle outer side is adjusted to improve the wear resistanceperformance. Furthermore, the sipes 34 formed in the block 100 in theintermediate region Mout on the vehicle outer side have thethree-dimensional structure in a range of 70% or more of the sipe lengthL1. Thus, with the sipes 34 provided, the reduction in the blockrigidity is compensated, so that the snow performance and the wearresistance performance can be improved in a well-balanced manner.

In the tire described above, the average land portion area Ain of theblocks 100 included in the intermediate region Min on the vehicle innerside and the average land portion area Aout of the blocks 100 includedin the intermediate region Mout on the vehicle outer side preferablysatisfy the relationship 1.5×Ain≤Aout≤3.0×Ain. With the ratio betweenthe average land portion area Ain on the vehicle inner side and theaverage land portion area Aout on the vehicle outer side thusappropriately set, the wear resistance performance and the snowperformance can be effectively improved.

When the average land portion area Ain on the vehicle inner side isexcessively larger than the average land portion area Aout on thevehicle outer side, the effect of improving the snow performance cannotbe sufficiently achieved. When the average land portion area Ain on thevehicle inner side is excessively smaller than the average land portionarea Aout on the vehicle outer side, the wear resistance performance islikely to be degraded.

The total sipe length Sin of the sipes 32 and 33 included in theintermediate region Min on the vehicle inner side and the total sipelength Sout of the sipes 34 included in the intermediate region Mout onthe vehicle outer side preferably satisfy the relationship1.3×Sin≤Sout≤2.0×Sin. With the ratio between the total sipe length Sinon the vehicle inner side and the total sipe length Sout on the vehicleouter side thus appropriately set, the sipe component in theintermediate region Mout on the vehicle outer side increases, so thatthe wear resistance performance and the snow performance can beeffectively improved.

When the total sipe length Sout on the vehicle outer side is excessivelygreater than the total sipe length Sin on the vehicle inner side, thewear resistance performance is degraded, or the snow performance isdegraded due to shortage of sipes on the vehicle inner side. When thetotal sipe length Sout on the vehicle outer side is excessively smallerthan the total sipe length Sin on the vehicle inner side, the effect ofimproving the snow performance cannot be sufficiently achieved.

The groove area ratio Rin in the ground contact region on the vehicleinner side and the groove area ratio Rout in the ground contact regionon the vehicle outer side preferably satisfy the relationship3%≤Rin−Rout≤8%. Setting a difference between the groove area ratio Rinin the ground contact region on the vehicle inner side and the groovearea ratio Rout in the ground contact region on the vehicle outer sideto the range described above allows the wear resistance performance andthe snow performance to be improved in a well-balanced manner whilemaintaining the dry performance and the wet performance.

When the difference does not fall within the range described above dueto the groove area ratio Rin in the ground contact region on the vehicleinner side set to be excessively high or low, the wear resistanceperformance and the snow performance cannot be improved in awell-balanced manner.

The sipes 32 and 33 formed in the intermediate region Min on the vehicleinner side and the sipes 34 formed in the intermediate region Mout onthe vehicle outer side are preferably inclined in opposite directionswith respect to the tire width direction. In other words, with the sipes32 and 33 formed in the intermediate region Min on the vehicle innerside and the sipes 34 formed in the intermediate region Mout on thevehicle outer side not being inclined in the same direction, variousbehaviors of the tire can be taken care of. Furthermore, the inclinationangle θ of the sipes 32 and 33 on the vehicle inner side (see FIG. 3A)and the inclination angle θ of the sipes 34 on the vehicle outer side(see FIG. 3B) preferably range from 20° to 65°. With the inclinationangle θ of the sipes 32 to 34 thus appropriately set, the snowperformance can be effectively improved.

The present technology can be suitably used for all-season tires usedthroughout the year and for winter tires. The hardness of rubber layerconstituting the tread portion 1 is preferably set to 65 or less. Thehardness is a durometer hardness defined in JIS (Japanese IndustrialStandard)-K6253 and is measured at a temperature of 20° C. using a typeA durometer.

Examples

Tires according to Conventional Examples 1 and 2, Comparative Examples 1and 2, and Examples 1 to 6 were manufactured as pneumatic tires having atire size of 225/65R17, including at least four main grooves extendingin the tire circumferential direction and a plurality of land portionsdefined by the main grooves in a tread portion with land portionslocated on the tire equator line formed of a block row or a rib row andwith a mounting direction with respect to a vehicle specified. In thepneumatic tires, the number of main grooves, presence of a center landportion, a symmetry of a tread pattern, the size relationship betweengroove area ratios R on the vehicle inner side and the vehicle outerside, the size relationship between average land portion areas A in theintermediate regions on the vehicle inner side and the vehicle outerside, the number of blocks Nin in the intermediate region on the vehicleinner side, the number of blocks Nout in the intermediate region on thevehicle outer side, the size relationship between total sipe lengths Sin the intermediate regions on the vehicle inner side and the vehicleouter side, the percentage of the three-dimensional structure of thesipes in the intermediate region on the vehicle outer side, the ratio ofaverage land portion area A in the intermediate region (Aout/Ain), theratio of total sipe length S in the intermediate region (Sout/Sin), thedifference in groove area ratio R (Rin−Rout), the inclination angle θ ofsipe in the intermediate region on the vehicle inner side, and theinclination angle θ of sipe in the intermediate region on the vehicleouter side were set as in Table 1.

In Table 1, regarding the size relationship between the groove arearatios R on the vehicle inner side and the vehicle outer side,“equivalent” means that the groove area ratios on the vehicle inner sideand the vehicle outer side are the same, and “inner side” means that thegroove area ratio Rin on the vehicle inner side is greater than thegroove area ratio Rout on the vehicle outer side. Regarding the sizerelationship between the average land portion areas A in intermediateregions on the vehicle inner side and the vehicle outer side,“equivalent” means that the average land portion areas on the vehicleinner side and the vehicle outer side are the same, and “outer side”means that the average land portion area Aout on the vehicle outer sideis larger than the average land portion area Ain on the vehicle innerside. Regarding the size relationship between total sipe lengths S inthe intermediate regions on the vehicle inner side and the vehicle outerside, “equivalent” means that the total sipe lengths on the vehicleinner side and the vehicle outer side are the same, “inner side” meansthat the total sipe length Sin on the vehicle inner side is greater thanthe total sipe length Sout on the vehicle outer side, and “outer side”means that the total sipe length Sout on the vehicle outer side isgreater than the total sipe length Sin on the vehicle inner side.

The snow performance and the wear resistance performance of these testtires were evaluated, and the results were recorded in Table 1.

Snow Performance:

For sensory evaluation regarding the steering stability performance onsnow-covered road surfaces and braking evaluation regarding brakingperformance on snow-covered road surfaces, the test tires were mountedon wheels having a rim size of 17×7.0 J, inflated to air pressure of 230kPa, and mounted on a four wheel drive vehicle, and test drive wasperformed by a test driver on a test course. Evaluation results areexpressed as index values, with the results of Conventional Example 1being assigned as an index value of 100. A larger index value indicatessuperior steering stability performance and braking performance onsnow-covered road surfaces.

Wear Resistance Performance:

The test tires were mounted on wheels having a rim size of 17×7.0 J,inflated to air pressure of 230 kPa, and mounted on a four wheel drivevehicle, and test drive was performed by a test driver on a test course.For the test drive, the estimated wear life was calculated after driving8000 km on the test course. Evaluation results are expressed as indexvalues, with the results of Conventional Example 1 being assigned as anindex value of 100. Larger index values mean longer wear life andsuperior wear resistance performance.

TABLE 1 Conventional Conventional Comparative Example 1 Example 2Example 1 Number of main grooves 4 4 5 Presence of center land portionYes Yes Yes Symmetry of tread pattern Symmetric Asymmetric AsymmetricSize relationship between groove Equivalent Inner side Inner side arearatios R on vehicle inner side and vehicle outer side Size relationshipbetween average Equivalent Outer side Outer side land portion areas A inintermediate region on vehicle inner side and vehicle outer side Numberof blocks Nin in intermediate 70 70 140 region on vehicle inner sideNumber of blocks Nout in 70 70 70 intermediate region on vehicle outerside Size relationship between total sipe Equivalent Inner side Outerside lengths S in intermediate regions on vehicle inner side and vehicleouter side Percentage of three-dimensional 0 0 0 structure in sipe inintermediate region on vehicle inner side (%) Ratio of average landportion area A 1.0 1.2 1.4 in intermediate region (Aout/Ain) Ratio oftotal sipe length S in 1.0 0.9 1.2 intermediate region (Sout/Sin)Difference in groove area ratio R 0 2.5 2.5 (Rin − Rout) [%] Inclinationangle θ of sipe in 15 15 15 intermediate region on vehicle inner side(°) Inclination angle θ of sipe in 15 15 15 intermediate region onvehicle outer side (°) Snow performance 100 95 97 Wear resistanceperformance 100 99 101 Comparative Example 2 Example 1 Example 2 Numberof main grooves 5 5 5 Presence of center land portion Yes Yes YesSymmetry of tread pattern Asymmetric Asymmetric Asymmetric Sizerelationship between groove Inner side Inner side Inner side area ratiosR on vehicle inner side and vehicle outer side Size relationship betweenaverage Outer side Outer side Outer side land portion areas A inintermediate region on vehicle inner side and vehicle outer side Numberof blocks Nin in 140 140 140 intermediate region on vehicle inner sideNumber of blocks Nout in 70 70 70 intermediate region on vehicle outerside Size relationship between total Outer side Outer side Outer sidesipe lengths S in intermediate regions on vehicle inner side and vehicleouter side Percentage of three-dimensional 45 85 85 structure in sipe inintermediate region on vehicle inner side (%) Ratio of average landportion area 1.4 1.4 2.0 A in intermediate region (Aout/Ain) Ratio oftotal sipe length S in 1.2 1.2 1.2 intermediate region (Sout/Sin)Difference in groove area ratio R 2.5 2.5 2.5 (Rin − Rout) [%]Inclination angle θ of sipe in 15 15 15 intermediate region on vehicleinner side (°) Inclination angle θ of sipe in 15 15 15 intermediateregion on vehicle outer side (°) Snow performance 98 101 103 Wearresistance performance 102 105 104 Example 3 Example 4 Example 5 Example6 Number of main grooves 5 5 5 5 Presence of center land Yes Yes Yes Yesportion Symmetry of tread pattern Asymmetric Asymmetric AsymmetricAsymmetric Size relationship between Inner side Inner side Inner sideInner side groove area ratios R on vehicle inner side and vehicle outerside Size relationship between Outer side Outer side Outer side Outerside average land portion areas A in intermediate region on vehicleinner side and vehicle outer side Number of blocks Nin in 140 140 140140 intermediate region on vehicle inner side Number of blocks Nout in70 70 70 70 intermediate region on vehicle outer side Size relationshipbetween Outer side Outer side Outer side Outer side total sipe lengths Sin intermediate regions on vehicle inner side and vehicle outer sidePercentage of three- 85 85 85 85 dimensional structure in sipe inintermediate region on vehicle inner side (%) Ratio of average landportion 2.0 2.0 2.0 2.0 area A in intermediate region (Aout/Ain) Ratioof total sipe length 1.5 1.5 1.5 1.5 S in intermediate region (Sout/Sin)Difference in groove area 2.5 5.0 5.0 5.0 ratio R (Rin − Rout) [%]Inclination angle θ of sipe 15 15 15 35 in intermediate region onvehicle inner side (°) Inclination angle θ of sipe 15 15 −15 −35 inintermediate region on vehicle outer side (°) Snow performance 104 106108 110 Wear resistance performance 103 105 105 105

As can be seen from Table 1, the tires of Examples 1 to 6 achievedimprovement in both snow performance and wear resistance performance,from those achieved by Conventional Example 1.

On the other hand, although Conventional Example 2 provides thebilaterally asymmetric tread pattern with respect to the tire equatorline, the number of blocks in the intermediate region on the vehicleinner side and the number of blocks in the intermediate region on thevehicle outer side are equivalent, and the sipes in the intermediateregion on the vehicle outer side had no three-dimensional structure,degrading snow performance. With Comparative Example 1, snow performancewas degraded, and sufficient wear resistance performance improvementeffect was unachievable, because the sipes in the intermediate region onthe vehicle outer side had no three-dimensional structure. WithComparative Example 2, snow performance was degraded, and sufficientwear resistance performance improvement effect was unachievable, becausethe percentage of the three-dimensional structure of the sipes in theintermediate region on the vehicle outer side was set to be low.

1. A tire, comprising at least four main grooves extending in a tirecircumferential direction and a plurality of rows of land portionsdefined by the main grooves in a tread portion, the land portionslocated on a tire equator line being formed of a block row or a rib row,a mounting direction with respect to a vehicle being specified, aplurality of lateral grooves extending in a tire width direction beingformed in an intermediate region between a main groove of the maingrooves located on an innermost side in the tire width direction and amain groove of the main grooves located on an outermost side in the tirewidth direction on a vehicle inner side of the tread portion from thetire equator line as a boundary and an intermediate region between amain groove of the main grooves located on an innermost side in the tirewidth direction and a main groove of the main grooves located on anoutermost side in the tire width direction on a vehicle outer side ofthe tread portion from the tire equator line as the boundary, thelateral grooves having a groove width of 2 mm or more and a groove depthof 50% or more of a maximum depth of the main grooves, the intermediateregion on the vehicle inner side and the intermediate region on thevehicle outer side each comprising 50 or more blocks defined by thelateral grooves, a plurality of sipes extending in the tire widthdirection being formed in each of the blocks in the intermediate regionon the vehicle inner side and the blocks in the intermediate region onthe vehicle outer side, a groove area ratio Rin in a ground contactregion on the vehicle inner side and a groove area ratio Rout in aground contact region on the vehicle outer side satisfying arelationship Rin>Rout, an average land portion area Ain of theintermediate region on the vehicle inner side and an average landportion area Aout of the intermediate region on the vehicle outer sidesatisfying a relationship Ain<Aout, the number of blocks Nin in theintermediate region on the vehicle inner side and the number of blocksNout in the intermediate region on the vehicle outer side satisfying arelationship Nin≥1.5×Nout, a total sipe length Sin in the intermediateregion on the vehicle inner side and a total sipe length Sout in theintermediate region on the vehicle outer side satisfying a relationshipSin<Sout, and the sipes formed in the blocks in the intermediate regionon the vehicle outer side having a three-dimensional structure in arange of 70% or more of a sipe length.
 2. The tire according to claim 1,wherein the average land portion area Ain in the intermediate region onthe vehicle inner side and the average land portion area Aout in theintermediate region on the vehicle outer side satisfy a relationship1.5×Ain≤Aout≤3.0×Ain.
 3. The tire according to claim 1, wherein thetotal sipe length Sin in the intermediate region on the vehicle innerside and the total sipe length Sout in the intermediate region on thevehicle outer side satisfy a relationship 1.3×Sin≤Sout≤2.0×Sin.
 4. Thetire according to claim 1, wherein the groove area ratio Rin in theground contact region on the vehicle inner side and the groove arearatio Rout in the ground contact region on the vehicle outer sidesatisfy a relationship 3%≤Rin−Rout≤8%.
 5. The tire according to claim 1,wherein the sipes formed in the intermediate region on the vehicle innerside and the sipes formed in the intermediate region on the vehicleouter side are inclined in opposite directions with respect to the tirewidth direction.
 6. The tire according to claim 5, wherein aninclination angle of the sipes formed in the intermediate region on thevehicle inner side and an inclination angle of the sipes formed in theintermediate region on the vehicle outer side range from 20° to 65°. 7.The tire according to claim 2, wherein the total sipe length Sin in theintermediate region on the vehicle inner side and the total sipe lengthSout in the intermediate region on the vehicle outer side satisfy arelationship 1.3×Sin≤Sout≤2.0×Sin.
 8. The tire according to claim 7,wherein the groove area ratio Rin in the ground contact region on thevehicle inner side and the groove area ratio Rout in the ground contactregion on the vehicle outer side satisfy a relationship 3%≤Rin−Rout≤8%.9. The tire according to claim 8, wherein the sipes formed in theintermediate region on the vehicle inner side and the sipes formed inthe intermediate region on the vehicle outer side are inclined inopposite directions with respect to the tire width direction.
 10. Thetire according to claim 9, wherein an inclination angle of the sipesformed in the intermediate region on the vehicle inner side and aninclination angle of the sipes formed in the intermediate region on thevehicle outer side range from 20° to 65°.